Combine graham cracker crumbs, melted butter and sugar. Press in a 8x12 pan and chill.
Combine milk and marshmellows in a heavy skillet or pan. Cook over medium heat, stirring often. When marshmellows are melted remove from heat. Cool to room temp. Whip 1 1/2 c. cream and fold into marshmellow mixture. Pour over cracker mixture. Pour cherry pie mix over top. It will drop down somewhat. Chill several hours or overnight. Serve with the 1/2 c. cream whipped or omit if you wish.